Thermally Reactive Ink Transfer System

ABSTRACT

An ink transfer system including an ink transfer decal that is transferable to a final substrate, such as a bare metal or pre-painted autobody part, without use of a separate adhesive. The transferred ink decal is capable of withstanding temperature elevations common during automotive paint baking without significant thermal degradation, discoloration, shrinkage or pealing.

BACKGROUND OF THE INVENTION

This invention relates to methods of transferring paint or ink to solidsurfaces and more particularly to a method of transferring asubstantially solid ink layer to a surface without the use of aseparately applied adhesive.

In the vehicle manufacturing industry, painted or inked designs aretypically applied through application of liquid paint to the surface ofa body element, such as a fender or hood. An example of this type ofapplication is pinstriping. Manual application of stripes or designsrequires artistic skill, even if the process is augmented through use ofstencils or tape. Airbrushed designs are very labor intensive andrequire considerable skill.

One prior art method of automating the application of designs or stripesis the use of adhesive decals. A decal is created by applying ink to aplastic film bearing adhesive on the opposite surface. The adhesive sideof the decal may then be applied to the desired surface. Furtherprotection may be achieved by applying a clear, protective, thermoset orphotoset coating over the surface to seal the decal against theelements.

These prior art decals have very limited elongation properties and aredifficult to apply to highly curved, edged or contoured surfaces.Further problems with prior art decals include separation of the decalfrom the substrate surface due to failure of the adhesive, andshrinkage, peeling and cracking of the decal itself over time. Inaddition, the decal typically presents a raised surface that can be feltand observed even after application of a clear coat. The raised decaldetracts from the overall appearance and makes the decal prone toincreased abrasion, chipping and peeling. Edges of prior on decals areprone to curl after exposure to heat during baking of a thermoset clearcoat.

BRIEF DESCRIPTION OF THE INVENTION

The present invention presents an ink transfer system including a decalthat may be subjected to high temperatures and UV radiation. The decalis provided as an alternative to hand painted detail trim for vehiclesand accessories such as automobiles, motorcycles, boats, boat motors andhelmets. The decal may be applied to various metallic, plastic orpainted surfaces and is particularly advantageous when applied topre-painted metal structures that are subjected to baking in order tocure overlying thermoset clear coats.

An ink transfer system according to the present invention may includeone or more layers of temperature and UV resistant ink deposited upon abacking sheet by screening or other currently known or later developedtechniques. If a waterslide decal is desired, the ink may be depositedupon waterslide decal paper having a water soluble coating. A transfermedium is deposited over the ink to aid in transfer of the ink to afinal receiving substrate. Because the ink is typically deposited uponthe backing sheet to form a thin film, the transfer medium aids transferof the decal from the backing sheet to the substrate without wrinklingor damaging the decal. The transfer medium may be applied over the inklayer through screen printing and it becomes an integral part of thetransfer system. Because the transfer medium is designed not to bond tothe ink, it is removed prior to application of a subsequent coating suchas a clear coat.

The decal exhibits high flexibility and elongation and may be appliedover contoured surfaces. Alternatively, the decal may be applied to aflat surface that is later bent, stamped or otherwise shaped.

Antioxidants and UV absorbers/light stabilizers are added to the baseresin to enhance heat and light stability and to increase tackiness andplasticity of the ink, particularly during heat curing of an overlyingclear coat material as is often the case in automotive applications.Although the decal is solid once formed, the ink comprising the decaladheres particularly well to metal and most painted and plastic surfacesdue to the low molecular weight polymers comprising the base resin(polymer vehicle). The addition of the antioxidants tends to suppresspolymerization enhancing the ability of the polymer vehicle to migrateinto the adjacent substrate and form a tight bond. The decal thereforeprovides a means for transferring solid ink to a substrate without theneed for a separate, intervening adhesive layer. When applied to apre-painted surface, the decal adheres to and binds with the underlyingpaint to form a uniform coating. Due to the thin layers of ink used toform the decal, the margins of the decal do not noticeably project abovethe substrate surface and are therefore unlikely to chip or peel,particularly if covered with a clear coating.

Other advantages of the invention will become apparent from thefollowing description taken in connection with the accompanyingdrawings, wherein is set forth by way of illustration and example,embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical cross sectional view of a decal formed in themanner described herein.

FIG. 2 is a diagrammatical cross sectional view of a decal formed in themanner described herein.

FIG. 3. is a top perspective view of a base coat applied to a backingsheet.

FIG. 4 is a top perspective view of an inked design applied over aportion of the base coat.

FIG. 5 is a top perspective view of a layer of transfer medium appliedto, and extending past the margins of, the inked design and base layer.

FIG. 6 is a top perspective view of a waterslide decal formed in themanner described herein, the edge of the backing sheet of the decalbeing positioned against a selected substrate prior to decal transfer.

FIG. 7 is a top perspective view of the decal of FIG. 6 in which thedecal has partially slid off of the backing sheet and onto the substratesurface.

FIG. 8 is a top perspective view of the decal of FIGS. 6 and 7 in whichthe decal has been fully removed from the backing sheet and has beenoriented in final position upon the substrate.

FIG. 9 is a top perspective view of the decal of FIGS. 6-8 in which thetransfer medium has been partially peeled away from the decal andsubstrate surfaces.

FIG. 10 is a top perspective view of the decal of FIGS. 6-9 in which thetransfer medium has been fully removed and the decal and substrate areready for application of a clear over coat.

FIG. 11 is a top perspective view of the decal of FIGS. 6-10 afterapplication of the clear over coat.

FIG. 12 is a diagrammatical cross sectional view of a decal formed inthe manner described herein.

DETAILED DESCRIPTION

As required, a detailed embodiment of the present invention is disclosedherein; however, it is to be understood that the disclosed embodiment ismerely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

An ink transfer system according to the present invention provides forthe application of liquid, polyurethane based inks onto a backing sheetto form an ink transfer decal. The decal is coated with a removabletransfer medium. The resultant decal is solidified, typically throughevaporation of diluents after application of each layer of liquidconstituent. It may then be removed from the backing sheet and appliedto a final substrate.

Through the use of low molecular weight aliphatic polymers andantioxidants for polymerization suppression, an ink is provided thatupon heating (during baking of a subsequently applied clear coat)becomes plasticized and tacky thereby obviating the need for applicationor use of a separate adhesive between the decal and the substratesurface. Due to the migration of low molecular weight polymers into thesubstrate surface, the decal binds to the substrate surface. In the caseof pre-painted surfaces, particularly those painted with polyurethanebased paints, the decal essentially becomes part of the painted coating.

The provision of a decal comprising thin films of high opacity ink ishighly beneficial as it enables rapid application of complex designs tosubstrate surfaces without the inefficiencies of hand painting whilealso avoiding problems related to prior art adhesive decals such aspeeling from the substrate due to failure of the adhesive; degradationupon subjection to elevated temperatures during baking of an overcoatsuch as a clear coat or finish; peeling, cracking or curling due toshrinkage; and increased subjection to abrasion or separation from thesubstrate due to projection of the prior art decal above the substratesurface. The ink transfer system of the present invention avoids thesedisadvantages by providing a thin film decal that self-bonds or adheresto the substrate and does not perceptibly project above the substratesurface. Indeed, upon proper application of the decal and subsequentcovering with a clear coat finish, no transition can typically be feltby touch or observed by the naked eye due to location of a decal of thepresent ink transfer system upon a typical substrate surface.

Decal Preparation

Referring now to the drawings, FIG. 1 illustrates a diagrammatical crosssectional view of a ink transfer system 100 formed in accordance withthe present invention for application of solidified ink to a substrate101 (see FIGS. 6-11), such as a painted automobile, motorcycle or boatbody panel or similar surface. The thickness of the various componentsare exaggerated in FIGS. 1 and 2 to aid in illustration.

The ink transfer system 100 includes a backing sheet 102 and transfermedium 104 enclosing transparent base coat 106 and pigmented ink 108layers, the latter two components comprising the ink transfer decal 109.The transfer medium 104 may also be referred to as a premask. The basecoat 106 and ink 108 may be referred to herein collectively as ink, inksor ink layers since the base coat 106 is formulated with similarconstituents as an ink and may be formulated generally as an unpigmentedink. In addition, the base coat 106 may comprise a pigmented ink ifenhanced opacity is required. The primary constituents and formation ofthe ink transfer system 100 are as follows. The backing sheet 102 has anupper surface adapted for receiving solvent-based polymer inks 108 andbase coats 106. An appropriate backing sheet 102 is formed of materialthat will accept the base coat 106 and ink 108 as they are screened uponthe sheet 102 without reacting with the inks or softening under theinfluence of the ink or ink diluents such as organic solvents. The uppersurface of the backing sheet 102 is typically provided with a thincoating of water soluble material that allows the decal 109 to be latertransferred to a substrate 101 using a waterslide technique.

Typically, although not necessarily, a base coat 106 is screen printedonto the backing sheet 102 to form an initial layer or coat that helpshold subsequent layers of pigmented ink 108 in proper position to oneanother. If layers of ink are physically separated from one another,such as with spaced bands 108 a, 108 b and 108 c of pinstriping as shownin FIG. 2, the base coat 106 provides a means for the individual bands108 a-108 c to be joined to one another to form a single ink transferdecal 109.

After the base layer 106 is applied it is dried to evaporate diluents,typically organic solvents. Next, one or more layers of pigmented ink108 are typically screened onto portions of the base layer 102.Typically, the pigmented ink 108 is applied so that a portion of thebase coat 106 extends beyond the margins of the pigmented ink 108. Ifthe substrate 101 to which the resulting decal 100 is to be transferredis dark in color, the base coat 106 may contain light-colored (such aswhite) pigment to provide an opaque, light background to enhance thebrightness of overlying layers of colored ink 108.

After solvents or diluents have substantially evaporated from the inklayer or layers 108, a release coat or layer 110 may be applied to coverand extend beyond the margins of the ink 108 and base 106 layers. Aswith the base coat 106, the release coat 110 may be formulated generallyas an upigmented ink 108. In addition, a release agent may be added tothe release coat 110 formulation to aid in the later separation of thetransfer medium 104 from the decal 109.

After solvents or diluents have substantially evaporated from eachprevious layer or coat, the transfer medium 104 may be applied over thebase coat 106, ink layers 108 and release coat or layer 110 (see FIGS.1, 2 and 12). The transfer medium 104 is typically applied so that itextends beyond the margins of the base layer 106, ink layer 108 andrelease coat 110. The transfer medium 104 is typically a clear, flexiblecoating that protects the decal 109 during storage and greatly aids thedimensional stability of the decal 109 during transfer to a substrate101 while still allowing sufficient flexion and elongation of the decal109 for application over, and conformation to, irregularly shapedsubstrate surfaces. As with the previously applied ink 108, base 106 andrelease 110 layers, the transfer medium 104 may be applied by screenprinting, rolling, spraying or other currently known or later developedtechniques. A coarser mesh may be used when screen printing the transfermedium 104 in order to deposit a somewhat thicker layer than wasdeposited when screen printing the base coat 106 and ink layer 108.FIGS. 1 and 2 illustrate the transfer medium 104 applied directly overthe ink 108 and base 106 layers. FIG. 12 illustrates a release layer 110disposed between the ink layer 108 and transfer medium 104. It should beappreciated that FIGS. 1, 2 and 12 are diagrammatical to show successionof component layers and do not reflect relative dimensions ofcomponents, particularly vertical dimensions or thickness. In addition,it should be appreciated that the component layers are appliedsuccessively as liquids and therefore conform closely to the underlyingsurfaces. For example, voids shown between spaced bands of ink 108 a,108 b and 108 c would in fact be filled by the transfer medium 104 andthe portions of the transfer medium 104 extending beyond the ink 108 andbase coat 106 layers would conform to exposed portions of the base coat106 and backing sheet 102, respectively.

After screen printing, the transfer medium 104 is dried to evaporatesolvents after which point the ink transfer system 100 has been formedand may be stored until required for transfer of the decal 109 to asubstrate 101. At each stage of solvent evaporation discussed above, thedecal 109 and transfer medium 104 may be dried, for example, by passingthe system 100 through a wicket cider or by inserting it into a dryingrack. Drying for one to two hours is typically optimal but decals 109may be produced with reduced dry times particularly if the decal 109 isexposed to increased air flow and mild heat such as with a blow dryerheld approximately six inches from the decal surface.

Any of the ink or base coat layers 108 and 106 may be transparent,translucent or opaque, however, the base coat 106 is typicallytransparent unless subsequent coats of ink 108 require an opaqueunderlying layer to allow the pigment of the ink 108 to more readilyshow against the color of the substrate. For example, if the decal 109is to be transferred to a dark colored substrate, a white or otherwiselight-colored base coat 106 may be desired so that the coloration ofsubsequent coats of pigmented ink 108 may be more apparent.

Decal Formulations

The following examples are provided to further disclose the invention.In these examples as well as throughout the specification and in theclaims, unless otherwise indicated, all parts and percentages are byweight. The constituents of the ink 108 and base coat 106 formulas areselected to provide improvements on the prior art such as heatresistance, chemical resistance, resistance to degradation due toexposure to light (particularly ultraviolet light), high flexibility andelongation characteristics, high tack (particularly during baking aftertransfer to a substrate) and self-adhesion.

In the first column in each table the components are identified. Thenext column provides the percent by weight of each component as aconstituent of the example formulation. The third column providesapproximate percent ranges for each component. These percent ranges donot represent limits for each component but are included as indicativeof preferable amounts. Should one or more components be substituted withan equivalent compound it is understood that the relative quantity ofthe other components may need to be adjusted to optimize the formulationfor a particular application or to enhance selected filmcharacteristics. It should be appreciated that evaporation of diluentsand/or solvents includes evaporation under ambient conditions as well asthrough application of heat and/or forced air.

By way of example, an initial vehicle (also referred to as a clearvarnish) may be prepared as a constituent of the base layer 106, as wellas of the pigmented ink layers 108, according to the followingformulation scheme:

TABLE 1 Vehicle Formulation Component % by weight range Thermoplasticpolyester polyurethane based resin 25 20-30 such as resins comprisingdiphenylmethane diisocyanate. Solvent system comprising: Ethyl 3ethoxypropionate 39 35-45 Cyclohexanone 19 15-25 Diacetone alcohol 1715-25

To prepare the vehicle, the solvent system is first prepared by mixingthe above solvents in an appropriate container. The resin is added tothe solvents and the contents of the container are heated to the meltingpoint of the resin, typically 100° F. to 140° F. The solvents and resinare stirred until the resin has melted and mixed thoroughly with thesolvent. The sides of the container may be scraped while mixing toinsure a homogeneous formulation.

The formulation of a clear base layer 106 may be prepared according tothe following formulation scheme. Note that the base layer 106formulation may be prepared essentially as unpigmented ink.

TABLE 2 Base Layer Formulation Component % by weight range Vehicle (seeabove) 92 85-95 Resin flow modifier such as Modaflow produced 2 1.5-2.5by Solutia Inc. UV absorbers such as substituted hydroxyphenyl- 3 1-4benzotriazoles, hydroxyphenyl-s-triazines, hydroxy-benzophenones andoxalic anilides, for example Tinuvin 1130 or Tinuvin 400. Hindered aminelight stabilizers such as those 1 0.5-1.5 derived from2,2,6,6-tetraalkyl piperidine, substituted piperizinedione, and/ordecanedioic acid, for example Tinuvin 123. A high molecular weightsterically hindered phenolic antioxidant such as: Irganox 1010 1 0.5-1.5Irganox 1035 1 0.5-1.5 Note: Tinuvin 1130, Tinuvin 400, Tinuvin 123,Irganox 1010, and Irganox 1035 are produced by Ciba Specialty ChemicalsCorporation.

Alternatively, a clear base layer 106 may be prepared without UVstabilizers and antioxidants as follows.

TABLE 3 Alternative Base Layer Formulation Component % by weight rangeVehicle (see above) 98.5 97.5-100  Resin flow modifier 1.5 1.0-2.5

As an example of a pigmented ink 108, a black pigmented ink may beprepared according to the formula set forth in Table 4. For othercolors, the percent of the selected pigment added may be modified asrequired to obtain the desired color and to increase or decrease opacityof the resultant ink.

TABLE 4 Pigmented Ink Formulation Component % by weight range Vehicle(see above) 76.3 50-90 Dibasic ester (solvent) 5 3-8 Black pigment 7.25-8 Resin flow modifier 1.5 1.5-2.5 Vehicle (see above) added as 10 0-10 required up to approximately 10% by weight to optimize viscosityand/or opacity.The solvent and pigment may be premixed with a smaller portion of thevehicle, such as 23% by weight, to aid in dispersion and solubilizationor suspension of the pigment. Typically, the premix is transferred forgrinding and dispersion of pigment in a three-roll mill. After thepremix has been ground in the mill to form a relatively homogeneousdispersion with particulates in the range of 0 to 3 microns, the premixis removed from the mill and mixed with the remaining clear varnish.

The percentages given for the black pigment are not necessarilyrepresentative for other pigment colors. For example, when preparing awhite Mk it may be advantageous to add white pigment in the range of 30to 50% of solids.

A top release coating or layer 110 may be applied over the ink layer108. A release layer 110 formulation may be formulated according to theformula described in Table 3 for the alternative base layer to comprise98.5% vehicle and 1.5% flow modifier. One or more additional componentsmay be utilized to enhance release of the transfer medium, for example arelease layer 110 formulation may comprise 95.55% weight vehicle asdescribed in Table 1, 1.45% weight flow modifier (such as the Modaflowproduct described above) and 3.0% weight release and flow agent. Anacceptable release and flow agent includes EFKA-7375 supplied by EFKAAdditivies B.V., the Netherlands.

Once formulated, the release layer 110 may be applied over the ink layeror layers 108 and dried, or allowed to dry, to evaporate the diluent.The release layer 110 is typically applied via screen printing and istypically applied to extend beyond the margins of the ink 108 and base106 layers. The release layer 100 increases the overall thickness of thedecal 109 and enhances the handleability and dimensional stability ofthe decal 109. The transfer medium 104 may then be applied over therelease layer 110, the release layer 110 remaining adhered to the inklayer 108 while enhancing release of the transfer medium 104 from thedecal.

Descriptions of Vehicle, Base Layer and Ink Components PolyurethaneResin

The above formulations include a thermoplastic polyester polyurethane asprepared in the vehicle formulation. Aliphatic polyurethanes such aspolyester polyurethanes are advantageous as they exhibit greaterstability in outdoor conditions because they tend to degrade less underexposure to weathering and UV light than aromatic polyurethanes. Linearpolyurethanes such as those employing 4,4′ diphenylmethane diisocyanate,4,2′ diphenylmethane diisocyanate and/or 2,2′ diphenylmethanediisocyanate can be formulated to yield a thermoplastic polyesterpolyurethane with high flexibility and elongation characteristics. Anappropriate commercial product includes Estane 5715 manufactured byNoveon, Inc.

UV Stabilizers

UV light can cause degradation and discoloration in ink films. UV lightis absorbed by constituent polymers causing bond cleavage and release offree radicals leading to depolymerization. In some cases, excessivecrosslinking also occurs causing embrittlement. Therefore, UVstabilizers such as UV absorbers and hindered amine light stabilizershave been added to the disclosed ink and base coat formulations toincrease longevity of the decals during exposure to outdoor light andthe high intensity UV radiation that may be used to cure photoreactiveover-coatings such as clear coats. UV absorbers such as substitutedhydroxyphenyl-benzotriazoles, hydroxyphenyl-s-triazines,hydroxy-benzophenones and oxalic anilides may be added to the ink andbase coat formulations. Examples of appropriate commercial productsinclude Tinuvin 1130 and Tinuvin 400 produced by Ciba SpecialtyChemicals Corporation.

Further protection from degradation due to UV radiation may be obtainedthrough the addition of hindered amine light stabilizers (HALS) such asthose derived from 2,2,6,6-tetraalkyl piperidine, substitutedpiperizinedione, and/or decanedioic acid. The HALS used with the aboveexemplary formulations comprisesbis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)-sebacate. Examples ofappropriate commercial products include Tinuvin 123 produced by CibaSpecialty Chemicals Corporation.

Antioxidants

Antioxidants such phenolic based anti-oxidants are used to hinderoxidation of ink 108 and base coat 106 polymers and in particular arehelpful to hinder thermally induced oxidation during exposure of thedecal 109 to elevated temperatures. In addition to protecting the decal109 during exposure to heat, the antioxidants suppress polymerizationduring curing at ambient temperatures thereby increasing the flexibilityand elongation characteristics of the decal 109 as well as essentiallyeliminating shrinkage and associated problems in the prior art such aspeeling and cracking. During baking of the substrate material, aftertransfer of the decal 109 and application of the clear over coat, thedecal 109 softens due to its thermoplastic qualities and takes onproperties of a resinous adhesive. At this time, the polymerizationsuppression of the antioxidants causes the ink 108 and base coat films106 of the decal 109 to become tacky and to bind to one another, thesubstrate 101 and the clear coat. Once baking of the clear coat iscompleted and the substrate 101 is allowed to cool to ambienttemperatures, the resultant finish comprises coatings that havesubstantially fused. Suitable phenolic antioxidants include3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene propanoic acid,2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]1,3-propanediylester and benzenepropanoic acid,3,5-bis(1,1-dimethylethyl)-4-hydroxy-,thiodi-2,1-ethanediyl ester.Suitable commercial antioxidant products for use in ink 108 and basecoat 106 formulations include Irganox 1010 and Irganox 1035 produced byCiba Specialty Chemicals Corporation.

Flow Agents/Modifiers

As indicated above, a flow modifier may be added to the base coat andink formulations. Flow modifiers, such Modaflow resin, enhance filmproperties by aiding in pigment dispersion, facilitating evaporation ofsolvents and release of entrained air, improving adhesion of the inkfilm 108 to the substrate 101 or prior ink coatings, including base coat106, and reducing surface imperfections of the cured decal films 109.

Flow modifiers increase the surface wetting and flow characteristics ofthe ink as it is screened on to the substrate, enhancing the ink'sability to self level to the substrate surface and enabling theproduction of thinner decal films 109. Flow modifiers are typicallyadded in the range of 0.1% to 2% of total resin solids but may beadjusted to levels outside of this range to optimize flowcharacteristics for a given ink formulation.

A solvent system comprising ethyl 3 ethoxypropionate, cyclohexanone, anddiacetone alcohol in the ratio disclosed in Table 1 may be used informulating the vehicle. Dibasic ester may be added to enhanceformulation of a pigmented ink.

Pigments selected to impart color to an ink should be selected forcompatibility with other ink components, in particular the polymerresin, and for other advantageous characteristics such as opacity,gloss, bleed resistance and resistance to thermal and light degradation.Examples of appropriate pigments for use in the disclosed inkformulations include pigments for liquid inks supplied by Sun ChemicalCorporation such as red pigment, product No, 228-0013, and violetpigment, product No. 288-0022 which are disclosed in product literatureas being heat fast to at least 500′.

Description of Transfer Medium

The transfer medium may be prepared according to the followingformulation scheme:

TABLE 5 Transfer Medium Formulation Component % by weight rangePropylene glycol methyl ether acetate (solvent) 40 25-50 Propyleneglycol methyl ether (solvent) 17 10-25 Diacetone alcohol 10  5-15 Resinflow modifier 3 1-6 Nitrocellulose 10  5-15 Polyvinyl acetate resin 2010-30

The transfer medium 104 is a film applied in liquid form over the basecoat 106 and ink 108 layers. After drying, the transfer medium 104enhances the handleability of the decal which would otherwise be quitethin and subject to folding over or wrinkling during transfer to thesubstrate 101. The transfer medium 104 is typically applied to form athicker film than the individual ink 108 or base coat 106 films. Thetransfer medium 104 disclosed in Table 5 is a film comprised ofpolyvinyl acetate and nitrocellulose that are formulated in a solventsystem comprising propylene glycol methyl ether acetate, propyleneglycol methyl ether, and diacetone alcohol. These solvents are selectedto solubilize and compatibilize the nitrocellulose and polyvinylacetate. A flow modifier (such as the Modaflow product described above)is added primarily to enhance surface wetting and flow characteristicsof the transfer medium formulation. The transfer medium 104 typicallydoes not contain additives to enhance UV or thermal stability because itis removed after application of the decal 109 to the final substrate 101and discarded.

Polyvinyl acetate, such as polyvinyl acetate beads from McGean, productno. ASB-516, are added to the transfer medium 104 as a binder and forimproved adhesion to metal and plastic surfaces. Other advantageouscharacteristics imparted or enhanced by the addition of polyvinylacetate to the formulation include thermoplasticity, flexibility,solubility in selected solvents, resistance to yellowing, glossiness,transparency, and resistance to oil, grease, and abrasion.

Nitrocellulose is a film forming polymer and enhances the ability of thetransfer medium 104 to become a thin, strong film upon curing. Ingeneral, polyvinyl acetate enhances the elasticity of the transfermedium film 104, while nitrocellulose enhances the rigidity and strengthof the transfer medium film 104.

An alternative embodiment of the transfer medium 104 may comprise arelease agent for enhanced release and separation of the transfer medium104 from the ink layer 108 or layers. This alternative transfer medium104 may be prepared according to the following formulation scheme:

TABLE 6 Alternative Transfer Medium Formulation Component % by weightrange Acrylic methacrylate resin 34.8 25-40 Plasticizer 10  7-12 Releaseagent 3 1-5 Solvent system comprising: Propylene glycol methyl etheracetate 33 25-35 Propylene glycol methyl ether 12.2 10-15 Diacetonealcohol 7  5-10

The alternative transfer medium formulation described in Table 6 iscomprised of an acrylic methacrylate resin, such as BR-201 (a butylmethacrylate thermoplastic acrylic resin) supplied by Dianal America,Inc., formulated in a solvent system comprising propylene glycol methylether acetate, propylene glycol methyl ether and diacetone alcohol.Typically, the solvent system is first prepared by transferringspecified solvents or equivalents to an appropriate mixing vessel. Aplasticizer and a release agent may then be added. An acceptablecommercial plasticizer includes Paraplex G-60 supplied by The C.P. HallCompany. An acceptable release agent includes Additol VXL 6383 suppliedby Signet Chemical Company. The solution is then heated to approximately140° F. or typically at least to the resin melting point (BR-210typically melts at temperatures from 110 to 120° F.). The resin is thenadded while mixing the solution and the resulting formulation is stirreduntil components are in solution and thoroughly mixed.

A further embodiment of the transfer medium 104 may be preparedaccording to the following formulation scheme:

TABLE 7 Alternative Transfer Medium Formulation Component % by weightrange Acrylic methacrylate resin 28.48 Plasticizer 8 Release agent 3Solvent system comprising: Propylene glycol methyl ether acetate 37.38Propylene glycol methyl ether 14.24 Diacetone alcohol 8.9

The alternative transfer medium formulation described in Table 7 iscomprised of an acrylic methacrylate resin, such as BR-201 (a butylmethacrylate thermoplastic acrylic resin) supplied by Dianal America,Inc., formulated in a solvent system comprising propylene glycol methylether acetate, propylene glycol methyl ether and diacetone alcohol.Typically, the solvent system is first prepared by transferringspecified solvents or equivalents to an appropriate mixing vessel. Therelease agent such as a silicone-free, fluorocarbon-modified polymer maythen be added and the solution mixed. The solution is then heated toapproximately 140° F. or typically at least to the resin melting point(BR-210 typically melts at temperatures from 110 to 120° F.). The resinis then added while mixing the solution, as is the plasticizer. Theresulting formulation is stirred until components are in solution andthoroughly mixed. An acceptable commercial plasticizer includes ParaplexG-60 supplied by The C.P. Hall Company. An acceptable release and flowagent includes EFKA-7375 supplied by EFKA Additivies B.V., theNetherlands.

Yet a further embodiment of the transfer medium 104 may be prepared byadding 3% by weight of the release agent identified above as Additol VXL6383 in accordance the following formulation scheme:

TABLE 8 Alternative Transfer Medium Formulation Component % by weightrange Acrylic methacrylate resin 27.52 Plasticizer 8 Release agent(EFKA-7375) 3 Release agent (Additol VXL 6383) 3 Solvent systemcomprising: Propylene glycol methyl ether acetate 36.12 Propylene glycolmethyl ether 13.76 Diacetone alcohol 8.6

Dispersion of solids in the above formulations may be evaluated using agrind block or smear test. Preferably, mixing is performed until solidsare tested as being under approximately 3 microns in size.

Decal Application/Transference of the Ink to a Substrate

Once formed, an ink transfer system 100 may be stored until needed. Thedecal 109 may be transferred to a final substrate 101, such as apre-painted automotive body part, according to the method or steps setforth below.

First, the ink transfer system 100 is trimmed, if desired, to removeexcess backing sheet 102 material. Generally, cutting or trimming of thetransfer medium 104 should be avoided unless it extends sufficientlybeyond the margins of the base coat 106 and ink layers 108 to allowremoval of excess. Next, the ink transfer system 100 is soaked in waterfor several minutes, two or more minutes generally sufficing forrelatively small decals. Extended periods of soaking should be avoidedas the water soluble coating on the backing sheet 102 may dissolvesufficiently to cause the decal 109 and transfer medium 104 layers tofall away from the backing sheet 102.

FIG. 6 is a top perspective view of the lower edge of the backing sheet102 positioned against a final substrate 101 with the ink transfersystem 100 facing the viewer. The decal 109 including the attachedtransfer medium 104 is then slid off of the backing sheet 102. In FIG.7, the decal 109 has been slid partially off of the backing sheet 102and onto the surface of the substrate 101.

At this point, the decal 109 is held together by the strong adhesion ofthe base coat 106, ink layers 108, and release coat 110 to one anotherand the weaker, though sufficient, adhesion of the transfer medium 104to the release coat 110. As indicated above, the transfer medium 104 isnot composed of the same material as the ink 108 and, although flexibleand capable of stretching, it is less so than the release coat 110, ink108 and base coat 106 layers since it is designed to provide dimensionalstability during transfer of the decal 109. For these purposes thetransfer medium 104 is also typically screen printed or otherwisedeposited to form a somewhat thicker layer.

The ink transfer decal 109 is applied to the substrate surface 101 withthe transfer medium 104 on top and the base coat 106 contacting thesubstrate surface 101. Due to the moisture on the decal 109 (thesubstrate may also be prewetted, for example by spraying with water froma spray bottle or hose, not shown) and the thinness and flexibility ofthe decal 109, the surface tension of the water between the decal 109and the substrate 101 causes the decal 109 to conform closely to thesubstrate surface 101 and to loosely adhere. At this point the decal 109may be moved or adjusted to its final position, often determined byregistration marks (not shown) on the substrate 101, and any wrinkles orbubbles may be smoothed out using a squeegee, sponge or otherappropriate device.

In FIG. 8, the decal 109 is shown fully removed from the backing sheet102 and placed in final position upon the substrate surface 101. InFIGS. 6 through 7, the dashed lines defining the ink 108 and base coat106 layers indicate that these layers are covered by and viewed throughthe transfer medium 104.

Because the ink 108 and base coats 106 are prepared from linear chainpolyester polyurethanes, and polymerization is somewhat suppressedthrough use of antioxidants, the ink 108 and base coat 106 films of thedecal 109 are extremely flexible and exhibit high elongationcharacteristics. Elongation of over 400% may be obtained when stretchingthe ink 108 and base coats 106. Because of these properties, the decal109 may be applied to molded surfaces having irregular shapes. Thetransfer medium 104 allows for stretching and other manipulation of thedecal 109 during application to the substrate 101 while aiding inhandling of the decal 109 which would otherwise be difficult due to theextreme thinness of the ink 108 and base coat 106 layers. In otherapplications, the decal 109 may be transferred to a relatively flatsurface for ease of registering and then subjected to considerablestretching and elongation due to bending or stamping of the piecepost-transfer.

The decal 109 is then allowed to dry through air drying or other means.After the decal 109 and transfer medium 104 dries and substantially allsurface moisture has evaporated, typically 1 to 24 hours after transfer,the transfer medium 104 may be peeled away from the deposited decal 109.FIG. 9 provides a top perspective view of the decal 109 showing aportion of the transfer medium 104 peeled away from the decal 109 andsubstrate 101. Because it is removed after the water between the decal109 and the substrate 101 has evaporated, it is important that thetransfer layer 104 not stick or bind to the decal 109 excessively. FIG.10 illustrates the decal 109 after removal of the transfer medium 104.At this point in the transfer process a clear base coat 106 may still beslightly visible or discernable from the surrounding surface of thesubstrate 101.

After 12 to 24 hours or air drying the water has typically evaporatedfrom the decal 109 and substrate 101 completely and a clear coat may beapplied. A commonly used, solvent-based, thermoset clear coat istypically applied by spraying. Such clear coatings often comprisethermoset polyurethanes that must go through a heat conversion tocomplete polymerization. Because of the extensive polymerization andcrosslinking such coatings typically provide very good chemicalresistance. As an alternative to a heat set system, a photoreactive (UV)coating may be applied.

FIG. 11 is a top perspective view of the decal 109 after application ofthe clear coat and baking. At this point in the ink transfer process,the decal 109 has fused to the substrate 101 and clear coat and, due tothe thinness of the base coat 106 and ink 108 layers, presents a designthat does not protrude or project above the adjacent finish.

The substrate 101 bearing the decal 109 and overlying clear coat is thenbaked in an oven or otherwise heated to temperatures typically in therange of 250 to 325 degrees Fahrenheit. Due to the presence ofantioxidants, the ink 108 and base coat 106 films may readily withstandexposure to such temperatures without degradation, discoloration,shrinkage, peeling or other defects. During the baking cycle the decal109 softens becoming fluid or semi-fluid. While heated the decal 109further polymerizes and adheres to compatible underlying surfaces suchas typical polyurethane-based paints and coatings used in the automotiveindustry. The softening and adherence characteristics of the decal 109are typically achieved as the temperature during the baking cycle risesto 185° F. and continue to improve as the temperature increases to 265°F. The decal 109 may be subjected to temperatures in excess of 375° F.

The ink film forming mechanism employed in the above ink embodiments ispartially that of a solvent evaporative coating yielding a thermoplasticink film. Film formation occurs during evaporation of the diluents andthe concomitant coalescence of the polymer chains. Polymerization toform linear, polyester-based polyurethane chains yields an ink filmhaving thermoplastic characteristics while still exhibiting goodresistance to solvents and other chemicals after curing.

Addition of Free Isocyanates to Enhance Polymerization and Cross Linking

If further chemical resistance, more complete polymerization and/orenhanced abrasion resistance of the base coat 106 and ink layers 108 isdesired, free isocyanates may be added to the ink formulation. Freeisocyanates with particular advantages include aliphatic polyisocyanateresins based on hexamethylene diisocyanate. Such compounds react wellwith polyester hydroxyl-functional coreactants such as are used toprepare the vehicle described in Table 1. Resultant coatings preparedusing polyisocyanate compounds exhibit enhanced resistance to solventsand oxidizing chemicals as well as increased abrasion resistance. Thecoatings have enhanced light stability, resistance to heat degradationand resist yellowing or other discoloration. A commercial productappropriate for providing free isocyanates with the above advantagesincludes Desmodur N 100, produced by Bayer Polymers LLC. Typically,these products are added to the ink formulation at levels of 0.005 to0.01% of resin solids.

As a further embodiment, a thermal set ink transfer system may beprovided through the addition to the ink 108 and base coat 106formulations of melamine and an acid catalyst. The melamine reacts withthe acid catalyst to form crosslinkages that set the film, reducing oreliminating thermoplasticity but increasing chemical and heatresistance.

It is to be understood that while certain forms of this invention havebeen illustrated and described, it is not limited thereto except insofaras such limitations are included in the following claims and allowableequivalents thereof.

1. A coating transfer system comprising: a flexible backing sheet havinga surface adapted to releaseably receive polymer resins; and an inktransfer coating printed upon a portion of said sheet, said ink transfercoating comprising a thermoplastic polymer resin, a UV stabilizer toinhibit photo degradation of polymers formed from said resin, and anantioxidant to inhibit oxidative degradation of polymers formed fromsaid resin, said ink transfer coating being releaseably received on saidsheet, said system being constructed without a separately appliedadhesive.
 2. The coating transfer system of claim 1, wherein said resincomprises a member selected from the group consisting of aliphaticpolyurethanes, polyester-based polyurethanes, the reaction product of atleast one diisocyanate and a polyol, and diphenylmethane diisocyanates.3. The coating transfer system of claim 1, wherein said resin comprisesat least one component selected from the group consisting of 4,4′diphenylmethane diisocyanate, 4,2′ diphenylmethane diisocyanate and 2,2′diphenylmethane diisocyanate.
 4. The coating transfer system of claim 1,wherein said UV stabilizer comprises a UV absorbing compound.
 5. Thecoating transfer system of claim 1, wherein said UV stabilizer comprisesa hindered amine.
 6. The coating transfer system of claim 1, whereinsaid UV stabilizer is selected from the group consisting of hydroxylsubstituted benzophenones and hydroxyl substituted benzotriazoles. 7.The coating transfer system of claim 1, wherein said UV stabilizer isselected from the group consisting of hydroxyphenyl-benzotriazoles,hydroxyphenyl-triazines, hydroxy-benzophenones and oxalic anilides. 8.The coating transfer system of claim 1, wherein said UV stabilizercomprises a hindered amine light stabilizer derived from a memberselected from the group consisting of 2,2,6,6-tetraalkyl piperidine, asubstituted piperizinedione, and decanedioic acid.
 9. The coatingtransfer system of claim 1, wherein said antioxidant comprises asterically hindered phenolic compound.
 10. The coating transfer systemof claim 1, wherein said ink transfer coating softens and adheres to areceiving substrate when said ink transfer coating is heated to atemperature between 185° F. and 375° F.
 11. The coating transfer systemof claim 1, further comprising a release layer deposited upon said inktransfer coating.
 12. The coating transfer system of claim 1, said inktransfer coating further comprising free isocyanate compounds.
 13. Thecoating transfer system of claim 1, said flexible backing sheet beingwater slide decal paper.
 14. The coating transfer system of claim 1,said ink transfer coating comprising one or more separately applied inklayers, each of said one or more ink layers being formed by printing asolvent-containing ink onto said sheet, said ink being capable of dryingby solvent evaporation at ambient conditions within one hour ofapplication to said sheet.
 15. The coating transfer system of claim 14,said ink transfer coating further comprising a transparent base coat inaddition to said one or more ink layers.
 16. The coating transfer systemof claim 1, wherein said ink transfer coating may be stretched toelongate greater than 400%.
 17. The coating transfer system of claim 1,wherein after removal of said backing sheet and after said ink transfercoating is placed in contact with a pre-painted substrate and heated toa temperature of 185° F. or above, polymers formed from said resinmigrate into said substrate thereby permanently bonding said inktransfer coating with said pre-painted substrate without a separatelyapplied adhesive.
 18. A method of transferring a solid ink design to asubstrate comprising the steps of: (a) providing a decal that does notinclude a separately applied adhesive, said decal comprising— (i) aflexible backing sheet having a surface adapted to releaseably receivepolymer resins, and (ii) an ink transfer coating comprising one or moreink layers and, optionally, a transparent base coat, each of said one ormore ink layers and optional base coat being printed onto said sheet asa liquid comprising a thermoplastic polymer resin, a UV stabilizer toinhibit photo degradation of polymers formed from said resin, anantioxidant to inhibit oxidative degradation of polymers formed fromsaid resin, and a solvent system, said liquid from which any of said oneor more ink layers and optional base coat are formed being capable ofdrying on said sheet by solvent evaporation upon being allowed to dryfor one hour at ambient conditions; (b) removing said flexible backingsheet from said decal to expose a surface of said ink transfer coating;and (c) applying said exposed surface to said substrate.
 19. The methodaccording to claim 18, said flexible backing sheet comprising waterslide decal paper.
 20. The method according to claim 19, step (b)including wetting said backing sheet prior to removing said backingsheet from said decal.
 21. The method according to claim 20, step (b)including removing excess moisture from between said ink transfercoating and said substrate.
 22. The method according to claim 21, step(b) including drying substantially all surface moisture from said decal.23. The method according to claim 1, said method further comprising: (d)applying a clear coat over said substrate and said ink transfer coatingafter step (c) with no raised transition between said substrate and saidink transfer coating being perceptible to the touch or to the naked eyeafter said clear coat application.
 24. The method according to claim 23,after step (d), baking said clear coat at a temperature of between 250to 325° F. thereby fusing said ink transfer coating to said substrateand said clear coat.
 25. The method according to claim 19, saidsubstrate being a surface of a vehicle or vehicle accessory.
 26. Themethod according to claim 19, said substrate being pre-painted prior toapplication of said decal.
 27. The method according to claim 19, saidsubstrate being a flat surface.
 28. The method according to claim 27,further comprising: (e) bending, stamping or otherwise shaping saidsubstrate surface after application of said decal thereby causing saidink transfer coating to stretch and elongate without cracking.
 29. Themethod according to claim 19, said surface being a contoured surface.30. The method according to claim 29, further comprising: (f) stretchingsaid decal over said contoured surface after removing said backing sheetwithout wrinkling or damaging the decal.